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GRAND CHALLENGE 4:
Create Efficient,
Healthy, Resilient
Cities
The future is increasingly urban. Cities will absorb almost
all of the worldâs projected population growth in the next three
decades. By 2050 cities will be home to over 2 billion more people
than today. The proportion of the worldâs population that lives in urban
areas will grow from 55 percent in 2017 to 66 percent in 2050.214 By 2030, 10
more cities are expected to cross the 10-million-inhabitant threshold for the first
time, increasing the number of âmegacitiesâ from 31 in 2016 to 41 in 2030. The
majority of these will be in lower-income countries and contain large slumsâdense
informal developments without government services.215
While this massive concentrated population growth is likely to further compound
many of the current problems that cities face, the urbanization of the human
population is happening at least in part because of the inherent attractiveness of
cities. They offer significant educational, economic, and cultural opportunities
as well as better access to communication and health care services. These
opportunities draw migrants from the rural countryside where such opportunities
are sparser. As noted in a 2016 United Nations report on urbanization, cities are
seen as economic hubs and drivers of innovation and competition, propelling a
steady flow of people from rural to urban areas, particularly in Asia.216
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Even as this economic attraction accelerates urbanization, todayâs cities face
persistent problems associated with air and water pollution, energy distribution,
water supply, waste disposal, and waste generation. Although cities only occupy 3
percent of Earthâs ice-free landmass, they produce 50 percent of global waste and
60 to 80 percent of global greenhouse gas emissions. Cities account for 60 to 80
percent of the worldâs energy use and 75 percent of all natural resource use.217
Cities have stark inequities in the distribution of incomes, public services, access to
open space, and quality of life. In middle- to high-income countries, urban sprawl
and car-centric and inefficient transit systems create traffic congestion, pollution,
and safety hazards, degrading quality of life. Lack of green space and abandoned
properties contribute to social and environmental stress, especially in poor urban
neighborhoods. Urban communities are fractured by poverty and unequal access
to community services, even as accelerating gentrification exacerbates those
inequities.
In low- and middle-income countries, large populations live in dense informal
settlements that are expanding rapidly; about 880 million people live in slums
today and that number is projected to more than double by 2050.218 With many
cities unable to provide adequate sanitation or food and water security for
these slums, their residents face a high risk of
malnutrition and disease.219 Increased human
contact with domestic animals and wildlife in
these settings heightens the risk of diseases with
pandemic potential that emerge from animals and
subsequently spread from person to person, as
occurred with the SARS epidemic. SARS spread
rapidly to more than 30 counties before being
contained.220
The functioning and stability of many of the worldâs
major cities are made all the more precarious by
threats from extreme events such as floods, heat
waves, and droughts, which are expected to hit cities
harder and more frequently in the coming decades,
putting more lives and infrastructure at risk.221
These challenges, however, are not insurmountable. The scale and structure of
cities offer unique opportunities to improve quality of life and equitably address
many of the grand challenges such as climate change adaptation, pollution, waste,
and sustainable food, water, and energy supplies. Aging physical infrastructure
represents both a major challenge and a key opportunity to reshape tomorrowâs
world. The American Society of Civil Engineers has estimated that $4.6 trillion in
U.S. infrastructure investment will be needed by 2025,222 and the Organisation for
Economic Co-operation and Development estimates worldwide infrastructure needs
at $70 trillion by 2030.223 If this infrastructure were refashioned to support multiple
city functions and the lives of residents in an integrated way, it is possible to create
cities that are more equitable, efficient, healthy, and resilient. Environmental
engineers can bring unique training and analytical skills to build partnerships with
the other professionsâin planning, energy, and transportation, among othersâ
who together can creatively overcome these challenges and take advantage of the
significant opportunities that cities present.
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What Does an Efficient City Look Like?
Cities can be viewed as urban ecosystems, composed of systems of infrastructure
networks (such as water, energy, transportation, waste, and public spaces), the
people who use and operate the infrastructure, and the multiple interactions that
occur between them. Accordingly, urban infrastructure is a system of systems
through which energy, money, information, and materials flow. Significant inequity
in the distribution of resources and political power within cities can result in
infrastructure systems that serve different communities to different degrees.
There are multiple ways to make cities more efficient, both by increasing the
efficiency of their individual parts and by making various systems function more
in concert with each other. For example, waste from one system can be used in
another system (waste to market or waste to energy), thereby minimizing inputs
and reducing net waste (see also Challenge 3). Documenting inequities in the
distribution of infrastructure services can help urban planners and engineers work
to address those issues. Two approaches to improve a cityâs efficiency involve
reenvisioning urban infrastructure and incorporating smart systems.
Reenvisioning Urban Infrastructure
Cities cannot achieve these desired efficiencies by simply monitoring and
improving the operations of older infrastructure. In the past, infrastructure systems
were designed to optimize water delivery, energy provision, transit, and land use in
a siloed fashion that led to suboptimal solutions. Going forward, sustainable urban
infrastructure development needs to look beyond the local scale and consider
transboundary infrastructures across regional, national, and global scales.224 For
example, developing reliable, nutritious, and sustainable food supplies in densely
populated cities requires looking beyond a cityâs boundaries to the full range
of producers, suppliers, and transporters and
the implications to energy and water use and
greenhouse gas emissions.
Cities can be more efficient by considering the
urban infrastructure as a system of systems at many
scales rather than individual disconnected entities
(energy, water, sanitation, and traffic). The design
of buildings and communities affects how much
energy and water are used and how much waste is
produced (Figure 4-1). Low-impact development
that mimics natural processes, for example
rain gardens and porous pavement, reduces
uncontrolled stormwater runoff and its associated
water pollution and erosion.225 It also provides
additional benefits such as added urban green space, reduced urban heat island
effects, and recreation opportunities. Improved management of urban stormwater
runoff increases nutrient and organic matter concentrations in wastewater, making it
easier to recover valuable resources, such as energy and nutrients. Urban aquaponic
systems, in which fish and plants are grown together, can recycle wastes and nutrients
while providing food security and eliminating food deserts.
Integrated urban solutions that address multiple needs or challenges can also help
save money. For example, in lieu of filtration to maintain water quality control
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FIGURE 4-1.â The Bullitt Center in Seattle is an example of a building designed to minimize its environmental impacts.
Constructed of local materials selected for their low health and environmental impacts, the building has solar panels
that generate as much energy as the building uses, employs geothermal heating and cooling, actively controls
windows and shades to optimize natural lighting and circulation of fresh air, stores rainwater for nonpotable use, and
has its own wetland to filter graywater.
of pathogens, for about 90 percent of its supply New York City uses watershed
protection strategies combined with chlorination and ultraviolet disinfection. This
approach up to the present time has allowed the city to save $8 billion to $10 billion
in capital expenses and approximately $1 million per day in operational costs as
compared to an engineered filtration-based approach for the entire supply.226
There are significant opportunities to transform urban infrastructure, but also
large challenges: most of the residential and commercial buildings and other
infrastructure in todayâs cities are old and inefficient, needing significant investment
to be maintained let alone enhanced. Older infrastructure is especially prevalent in
the poorest urban communities, further exacerbating inequities. This transformation
to efficient, sustainbable urban infrastructure âand the contributions of
environmental engineers to that transformationâwill need to address head-on how
to apply those changes not just to new buildings and infrastructure, but to adaptive
reuse and revitalization in all city neighborhoods.
Advancing Smart Cities
Improvements in efficiency can also be gained through âsmartâ technologies
that capitalize on advances in sensing technology, data, connectivity, artificial
intelligence, and participatory governance to optimize operations and resource
management.227 A smart system can be not only reactive but proactive, using
inputs, information processing, intelligence, and actuation to anticipate and prevent
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BOX 4-1. DESIGNING SMART SYSTEMS
Smart systems are being developed to improve city functions, as demonstrated by these examples. Such systems can
become more predictive and require less human involvement as technology improves and smart systems are more
effectively integrated into city operations.
â¢â start-up company is applying artificial intelligence to help cities efficiently respond to earthquakes by predicting,
A
in real time, which areas are likely to have suffered the most damage and where injured people are likely to be
concentrated. 231
â¢â Barcelona, sensors provide site-specific weather information that is used to calibrate the precise amount of water
In
needed to irrigate parks. 232
â¢â Amsterdam, a mobile app allows cyclists to turn up the intensity of outdoor lighting while they ride along a bike path
In
and then let the lights dim after they pass through, allowing residents to play an active role in helping the city operate
efficiently. 233
â¢âmart grid technology in being implemented to improve efficiency and avoid cascading failure, as happened in the 1996
S
western United States blackout. 234
â¢âmart waste management systems monitor how full bins are and use solar power to compress waste before pick-up,
S
helping managers plan waste collection routes for greater efficiency. 235
Smart systems are not limited to cities in higher-income countries; low- and middle-income countries have begun to âleap-
frogâ over older technologies to take advantage of newer ones:
â¢â collaboration between the World Bank, the ride-hailing platform Grab, and the government of Cebu City, the Philippines,
A
allows the city government to use GPS data from taxi driversâ smartphones to track traffic patterns and incidents and
inform emergency response and transportation planning. 236
â¢ân app developed for residents in Rio de Janeiro, Brazil, uses crime data and machine learning to predict where and
A
when crimes are most likely to occur, allowing users to make informed decisions and reduce their risk as they move
throughout the city. 237
problems or inefficiencies.228 Although there are many ways to define a âsmart city,â
the basic idea is that cities can improve outcomes, such as efficiency or quality of
life, by incorporating smart interconnected systems into municipal functions.229
Technological advancements are increasing opportunities to develop smarter cities.
Improvements in sensing technology have made it feasible to collect detailed
geospatial and other types of data on the systems that keep cities ticking, such as
transportation patterns and water and energy use. When appropriately analyzed
and connected to decision making or operational controls, these data can be a
powerful asset to improve city functions and planning. Developments in data
science and machine learning are advancing these capabilities; a 2018 report by
the World Economic Forum230 identified artificial intelligence as a key technology
for efforts to transform traditional sectors and systems to address climate change,
deliver food and water, protect biodiversity, and bolster human well-being.
Smart systems are being tested in cities around the world. To date, most of these
tests focus on isolated sectors, such as transportation, emergency response, or
electricity distribution (see Box 4-1), although some projects are experimenting
with combining multiple smart systems across a community (see Sidebar).
Despite these encouraging developments, adaptive, full-scale predictive smart
cities are still a long way off. Questions around performance, control, security,
economics, equity, and ethics in smart cities must be addressed in order to fully
realize the complete suite of societal benefits.241 In addition, while sensors and
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DEVELOPING SMART COMMUNITIES
Smart communities that combine multiple smart systems are to reduce energy demands. Autonomous shuttles, cycling,
being planned around the world. One such planning effort is and walking would be the primary means of transit. Sidewalk
underway in Toronto in a formerly industrialized area along snow melters and automated awnings would keep bike-share
the waterfront, called Quayside. Sidewalk Labs, a subsidiary stations, transit stops, and cycling and walking paths useable
of Alphabet, is planning to take a 12-acre plot and create the through the winter.
âworldâs first neighborhood built from the Internet up,â238 with Sensor deployment and data acquisition represent the
flexible mixed-use space and housing for about 5,000 people backbone of the Quayside project vision. Sensors would
(Figure). 239 measure everything from air pollution and noise to sewage
Some of the smart features envisioned at Quayside include flow rates to how often a public waste bin is used. 240 The
a carbon-neutral thermal grid that would use geothermal design process was launched in 2017 and Sidewalk Toronto is
energy, waste heat, and energy generated by anaerobic working with experts and stakeholders to co-create the final
digestion of organic waste to heat and cool buildings, neighborhood design plans.
combined with rigorous building construction standards aimed
DIGITAL
Digital Layer
BUILD
Buildings
PHYSICAL LAYER
Mobility MOB
Public Realm
PUBLIC
Infrastructure
INFRASTR
A NEW KIND OF NEIGHBOURHOOD 19
FIGUREâ A vision for Quayside, a mixed-use urban development in Toronto. The design process was launched in 2017.
Create Efficient, Healthy, Resilient Citiesâ |â 59

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tools for citizen participation are being actively developed, implementationâ
effectively integrating real-time information and feedback into actual city
operationsâremains a challenge.242 These challenges are not mere technological
hurdles; overcoming them will require deep understanding of the physical and
social systems that are integral to city functions, as well as a deeper understanding,
on the part of engineers and city managers, of the opportunities and limitations
of the technology. Furthermore, there is a need not only to continue to develop
and scale tools for collecting data, but also to facilitate the effective and equitable
application of such information. This will require interdisciplinary efforts to manage
and interpret data, a willingness and capacity to adapt city operations to changing
circumstances, and adequate protections for privacy and security.
What Makes a City Healty?
Healthy cities facilitate good health and promote a high quality of life for all
their residents. Healthy cities support mental and physical health, providing
residents sufficient and equitable access to community services, education,
housing, art, clean rivers, recreation, and green space, as well as protection from
crime, violence, and hazardous environments. Clean air, safe drinking water and
sanitation, effective and affordable transportation, reliable access to power, ample
opportunities for employment, and access to nutritious food and health services are
important facets of a healthy city.
Healthy buildings are a critical component of healthy cities because people
spend over 90 percent of their time indoors.243 Healthy buildings are constructed
of materials that do not off-gas toxic compounds into the air. They feature
ventilation and lighting designed to optimize productivity and well-being, while
also conserving energy. Designing buildings for health, well-being, and water and
energy conservation can sometimes involve trade-offs to optimize for competing
needs. For example, a tightly sealed building is more energy efficient with respect
to temperature control, but it also allows build-up of contaminants in air. Likewise,
technologies and practices designed to save water and reduce energy used for
heating water may inadvertently promote the spread of pathogenic microbes.244
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The capacity to prevent, detect, and mitigate
the spread of infectious disease is particularly
vital to healthy cities, but it will become
more difficult to establish and maintain this
capacity as cities and slums grow larger and
denser. Many emerging diseases result from
transmission of infectious agents from animals
to people.245 These trends underscore the
need to take a holistic view of public health
that encompasses the health of humans,
animals, and the environment, a concept
and approach known as One Health.246 Two
important infectious disease challenges are
the emergence of diseases with pandemic
potential and the emergence of antibiotic-
resistant pathogens.247 Although these challenges are not uniquely urban, many
infectious disease problems could be exacerbated in cities and spread through
connected suburban communities.
Sophisticated techniques such as culture-independent diagnostics, genomic
analysis, and advanced epidemic modeling offer valuable tools to track and
contain the spread of pathogens and antibiotic-resistant organisms. Yet, these tools
cannot make up for a lack of basic infrastructure to deliver clean air, safe food
and water, sanitation services, and reliable electricity to homes and health care
facilities. The knowledge and technology to mitigate many of the environmental
drivers of infectious disease and other public health threats exist, but there are
significant gaps in infrastructure and services, especially in the poorest areas. This
disparity points to a need for more efficient, scalable solutions to support public
health, including measures to prevent and contain infectious diseases along with
improvements to the broader social and physical environments of the worldâs cities.
Innovative solutions have been proposed to apply technologies and policies to
improve public health in low-income settings. In Africaâs largest urban slum (Kibera
in Nairobi, Kenya), integrated âbiocentersâ are being used to capture waste and
digest it into biogas, which can be used as cooking fuel, thereby helping to manage
waste while simultaneously reducing exposures to both outdoor and indoor air
pollution from traditional cooking with wood, dung, and charcoal.248 The Diesel
Emissions Reduction Act249 has provided grant funding and other incentives to
support clean diesel projects, helping to replace old diesel school buses in low-
income communities in Houston with low-emission models, reducing childrenâs
exposure to pollution from diesel exhaust. With new emission standards and
advances in technology, the percentage of low-income populations in the United
States that live with air quality above the current fine-particulate standards dropped
from 57 percent in 2006-2008 to 8 percent in 2014-2016.250
What Makes a City Resilient?
Resilient cities have the capacity to endure disasters, whether they are economic,
environmental (such as floods, earthquakes, or drought), or the result of terrorism.
To be resilient, cities must have the ability to withstand stress and quickly recover
or adapt. One way to accommodate stress is to have redundant systems, for
example, in utilities such as power or water grids or transportation routes, to
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support continued operations when the primary system is not functional. Resilience
also means being able to mobilize resources quickly in response to a disruptive
event and contain the amount of damage caused. Resilience encompasses
preparation, response, recovery, and adaptation.
Increasing a communityâs resilience can involve repurposing existing systems
or creating infrastructure that serves multiple purposes. Bostonâs Muddy River
Restoration Project restores riparian habitat to reduce the severity of flooding
events.251 The project discourages development in flood-prone areas, reducing the
damage, displacement, and disruption associated with future floods. In the wake of
significant flooding, Copenhagenâs Ãsterbro neighborhood is creating a network of
green streets and neighborhood park stormwater retention areas that will make the
neighborhood more resilient to future storms.252
To increase resilience, it is important to systematically assess current vulnerabilities
to inform better design. Such assessments can be used to prioritize measures for
addressing vulnerabilities through existing and planned systems and infrastructure.
Climate science provides one input into such an assessment. For example, planners
can use decision tools to examine the range of potential infrastructure impacts
associated with future climate scenarios, projecting threats such as sea-level rise,
drought, and extreme heat. Planners also need to look at anticipated shifts or stressors
that are likely to affect a cityâs ability to respond to such events. For example, it may
be important to assess transportation patterns and factors that may influence the
number and use of vehicles. As a cityâs population rises, dramatic increases in the
number of vehicles could overwhelm infrastructure and necessitate the replacement
of open lands with parking areas and buildings that would exacerbate flooding and
increase heat island effects. On the other hand, a significant increase in the use
of shared vehicles, as might occur with autonomous vehicles, could eliminate 90
percent of parking demand,253 thereby reducing projected flood risk and allowing the
repurposing of parking space for the creation of green space.
Many cities are actively pursuing sustainable, multipurpose solutions like those
in Copenhagen and Boston, but the scale of these projects is often not aligned
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with the full scale of the challenge, and
there remains much room for improvement
toward understanding risks and building more
resilient structures, systems, and communities.
In addition to research and technological
solutions, becoming resilient requires a cultural
shift among decision makers, stakeholders, and
citizens. By better assessing, understanding, and
communicating risk, cities can garner support
for forward-looking resilience goals and the
steps needed to achieve them.
What Environmental
Engineers Can Do?
In general, efficient, healthy, resilient cities will not be built from scratch. Rather,
the challenge is to incorporate new designs and systems into existing cities and
their infrastructure. This means actively reengineering existing land-use patterns,
built environments, and water, sewer, electricity, and transportation modalities and
infrastructure. Whatâs more, cities must undertake these efforts at the same time
as they are absorbing massive population growth, that stresses current systems
as new ones are established. This will undoubtedly be a complex process, and
implementing effective solutions will require research and coordination involving
multiple disciplines and sectors. Research is needed to identify and prioritize key
vulnerabilities that cities face and effective adaptations that they should undertake.
These efforts should include gleaning lessons from cities that have begun such
transitions, as well as finding innovative ways to engage both the private sector,
which has significant sway over the state of the built environment, and the public
sector, which typically leads the way on infrastructure.254
Creating efficient, healthy, resilient cities involves many overlapping considerations
from the challenges discussed previously in this report. The solutions will require
leadership, systems thinking, and innovation from environmental engineers working
with the many other professionalsâin planning, transportation, energy, and public
health, among othersâto create and implement successful urban solutions. In
particular, the tools of environmental engineering will be invaluable in applying
sensors strategically, building distributed systems, and improving the design of
cities. See Box 4-3 for specific examples of ways that environmental engineers can
work to create efficient, healthy, resilient cities.
Applying Sensors Strategically
Sensors are key to smart, responsive cities and are particularly valuable for
conserving resources and increasing livability and safety. Traffic-monitoring sensors,
for example, can be used to change signal patterns to relieve congestion in real
time or inform long-term solutions to more systemic traffic issues, thus reducing the
amount of energy wasted, pollution generated, and productivity lost in traffic jams.
Similarly, sensors that collect data on water or energy use can help individuals
minimize their consumption of these resources and inform how utility companies
manage and deliver them or respond to disruptions. Systems that monitor chemical
or biological contaminants in air, water, food, and human populations can provide
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BOX 4-3. EXAMPLE ROLES FOR ENVIRONMENTAL ENGINEERS TO CREATE EFFICIENT, HEALTHY,
RESILIENT CITIES
The following are examples of ways that environmental engineers, working collaboratively with other disciplines, can
engage with the public and private sectors to help build efficient, healthy, resilient cities. In doing so, environmental
engineers can ensure as well that solutions like those highlighted below are designed and implemented in ways that are
fully cognizant ofâand help to addressâthe significant current inequitable distribution of services in todayâs cities.
â¢âesign and revitalize infrastructure systems, including water, energy, food, buildings, parks, and transportation systems,
D
to achieve equitable access and optimize among sometimes competing objectives for health, well-being, water and
energy conservation, and resilience.
â¢âvaluate the potential positive and negative consequences from alternative infrastructure designs, including impacts to
E
pollution, energy consumption, and greenhouse gas emissions.
â¢âddress extraordinary infrastructure challenges in low-income country settings by developing and evaluating innovative
A
approaches to address water, sanitation, and health challenges unique to urban and periurban slums.
Identify opportunities in cities and design systems for capturing and repurposing waste (solid waste, wastewater, and
â¢â
heat) for energy or resource recovery, considering both large, centralized and small, decentralized systems.
â¢âevelop and use sensors to support more efficient city operations, including transportation, water and wastewater,
D
energy, environmental quality, and public health. This includes working to develop artificial intelligence decision-making
algorithms for smart cities and working, in collaboration with social scientists, to engage citizens in the development and
refinement of these algorithms.
D
â¢âevelop and evaluate innovative approaches to reducing indoor and outdoor air pollution.
early warning of emerging health threats. Sensor technology is developing rapidly
and in many cases is now good enough and cheap enough for widespread use;
the question is, how can these technologies be deployed and utilized through
applications of artificial intelligence algorithms to enable efficient operations at the
scale of a city?
Building Distributed Systems
Although many of todayâs cities are built with centralized systems for water, energy,
and waste, distributed systems could make cities both more efficient and more
resilient. For example, buildings or city blocks can generate their own electricity
by incorporating renewable sources such as solar, wind, biomass, or wastewater.
Or, they can reduce their reliance on centralized water supplies by collecting
graywater, rainwater, or cooling water and using it for nonpotable purposes.255
Multimodal systems, such as combined cooling, heating, and power systems, use
the waste heat from electricity generation to heat or cool buildings; these systems
can be twice as efficient as separate systems256 and also reduce greenhouse gas
emissions, air pollutants, and water consumption.257 A city with a combination of
centralized and distributed systems also means that, in a time of disaster, people
live closer to the services they need and are less heavily impacted by disruptions
that occur elsewhere in the city. These same distributed systems could also be
customized for use in rural areas, providing access to services that are costly to
deploy in areas with low population density.
Although there are now many emerging technologies and models to support
distributed systems, environmental engineering expertise is needed to determine
which solutions are most practical, resource efficient, and appropriate for different
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circumstances and to optimally integrate these solutions into
existing city infrastructure. At the same time, it is important
to continue to develop, optimize, and apply distributed
solutions to address the anticipated demands and needs
of future cities. To ensure that these solutions are practical
and palatable for communities, environmental engineers
will also need to be trained to look beyond the technology
opportunities and understand perceived and real unintended
impacts, such as noise and emissions, which have stymied
previous efforts to distribute energy generation in cities.
Improving City Design
Revising the design of cities will be necessary to
accommodate more people in a way that improves rather than harms quality of
life. Connectivity is one important element. Connecting people from all economic
strata to basic goods and servicesâfrom clean water and reliable electricity to
groceries and health care to employmentâimproves equity, health, and resilience.
Improving infrastructure for active transportation (walking and cycling) can enhance
health and reduce congestion, energy use, and pollution. Optimizing the design of
buildings and public spacesâand identifying ways to build those principles into the
revitalization of existing buildings and public spacesâis another key goal that can
reduce resource consumption and improve environmental quality and quality of life.
Adapting to climate-related changes and designing for resilience will be key to
sustaining cities and their populations in the coming decades. Such adaptations
often can serve multiple purposes; for example, equitably distributed green space
can promote well-being,258 while also mitigating natural disasters by absorbing
floodwaters and recharging aquifers. Stakeholder engagement is paramount to
ensure citizen support for new city designs (see Challenge 5). By identifying,
prioritizing, and implementing solutions that will reap multiple benefits,
environmental engineers can make significant contributions toward building more
efficient, healthier, and more resilient cities.
Create Efficient, Healthy, Resilient Citiesâ |â 65

Environmental engineers support the well-being of people and the planet in areas where the two intersect. Over the decades the field has improved countless lives through innovative systems for delivering water, treating waste, and preventing and remediating pollution in air, water, and soil. These achievements are a testament to the multidisciplinary, pragmatic, systems-oriented approach that characterizes environmental engineering.

Environmental Engineering for the 21st Century: Addressing Grand Challenges outlines the crucial role for environmental engineers in this period of dramatic growth and change. The report identifies five pressing challenges of the 21st century that environmental engineers are uniquely poised to help advance: sustainably supply food, water, and energy; curb climate change and adapt to its impacts; design a future without pollution and waste; create efficient, healthy, resilient cities; and foster informed decisions and actions.

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